Fighting condensation in home

December 19th 2012
Fighting condensation in home

Your energy efficiency upgrades may be causing havoc within your home when the cold weather shows up and here is why.


The three major upgrades include the furnace, windows and insulation & draft proofing in the attic. The havoc I relate to is condensation on the inside of your new windows even though you replaced your old aluminum framed windows with vinyl framed windows.


1. Your new high efficient furnace no longer takes combustion air from the basement or furnace room area, removing moist air which has settled in the furnace area through the combustion process thus reducing the moisture in the home.  New high efficient furnaces draw the required combustion air through plastic pipes from the outside directly to the combustion chamber as well as having a continual flow furnace fan to maintain a balanced ambient temperature.


2. Windows – New vinyl windows if installed properly are tight and sealed to the house envelop to stop drafts as well as any excess high humidity (moisture) from being exhausted out around the old aluminum or wood frames.


3. Insulation and Draft Proofing – Many home owners had insulation upgrades in their attics with “NO” draft proofing. Draft Proofing is done before the insulation upgrades are complete by caulking and sealing around, electrical house wiring coming up through partition and exterior walls of the home, sealing around vent stacks, light fixtures, plumbing stacks, chimney stacks and exhaust ventilation ducts. When draft proofing is overlooked a sign would be the dark stains on the underside of roof sheathing in the attic cavity. This movement of air containing moisture is pushed into the attic cavity by the forced air furnace when in operation pressurizing the home and pushing air anywhere there is a weakness in the envelope.


Taking all three upgrades into consideration and reviewing your home as a system, the question now becomes - what did you do about the high humidity building up inside your home if you didn’t address the exhaust ventilation in the bathroom, kitchen and any moisture created within the home?


Dehumidistat: A dehumidistat is a device to operate a ventilation system such as a bathroom fan or an HRV (Heat Recovery Ventilation) to exhaust the excess humidity out of your home. The setting of this unit is determined by the outside air temperature (see chart below)

Relative humidity should be as follows;    Summer time is 50% to 60%
Outside Temperature             Living Temperature Inside              Relative Humidity (Inside Home)
Above 0°C                                21°C                                                  40%
-5°C                                          21°C                                                  35%
-10°C                                        21°C                                                  30% 
-20°C                                        21°C                                                  25%
-30°C                                        21°C                                                  20%